Hey Cliff,
I have never found a belt keeper on a belt dated before 1904. That doesn't mean they weren't made, just that I've never seen a photo or sample of one. They were probably the exception rather than the rule. However, in saddles, I've seen the most uncomfortable saddles are the ones that didn't get used to death. So, in the case of saddles, the poorly made ones were the ones to survive in larger numbers, because they weren't ridden to pieces like the good ones.
In many of the old photos, you will see the belt hangs at an odd angle at the buckle, sometimes with the end of the belt hangin' down. Since I got my start in the leather business makin' belts for modern shooters, and they didn't like their belts hangin' down, that's what I mostly made for 'em. When I started makin' patterns, I just made what folks want. If you wanted to best represent what was common in the old west, leave off the keeper and let the belt hang at an odd angle.
All of my patterns are authentic. You may not want to reproduce the gear they represent, but that has nothin' to do with authenticity. There were other ways of makin' the same thing. I just didn't make patterns for 'em that way.
The great thing about a pattern is, you can use it as a startin' point and make it your own by addin' or takin' away aspects of it. I rarely use my own patterns when I'm makin' somethin' for me. I copy something specific I've seen in a museum or in a book. But, a guy can't make a livin' makin' 457 different patterns. It takes me over a month to put together a pattern pack. It takes me years to earn that money back in sales. They only solution is to make a basic set of patterns and let folks modify 'em to suit themselves.